[Bug middle-end/93505] [8 Regression] wrong code or ICE with __builtin_bswap64() and rotation at -Og

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93505

--- Comment #21 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-8 branch has been updated by Jakub Jelinek
<jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:a73ee641c3d2ca729bdf55225afd881f57bf4d96

commit r8-10013-ga73ee641c3d2ca729bdf55225afd881f57bf4d96
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Feb 14 15:46:13 2020 +0100

    combine: Punt on out of range rotate counts [PR93505]

    What happens on this testcase is with the out of bounds rotate we get:
    Trying 13 -> 16:
       13: r129:SI=r132:DI#0<-<0x20
          REG_DEAD r132:DI
       16: r123:DI=r129:SI<0
          REG_DEAD r129:SI
    Successfully matched this instruction:
    (set (reg/v:DI 123 [ <retval> ])
        (const_int 0 [0]))
    during combine.  So, perhaps we could also change simplify-rtx.c to punt
    if it is out of bounds rather than trying to optimize anything.
    Or, but probably GCC11 material, if we decide that ROTATE/ROTATERT doesn't
    have out of bounds counts or introduce targetm.rotate_truncation_mask,
    we should truncate the argument instead of punting.
    Punting is better for backports though.

    2020-01-30  Jakub Jelinek  <jakub@redhat.com>

        PR middle-end/93505
        * combine.c (simplify_comparison) <case ROTATE>: Punt on out of range
        rotate counts.

        * gcc.c-torture/compile/pr93505.c: New test.